Apparatus for optically monitoring a dosing of a liquid to be pipetted

ABSTRACT

The invention relates to an apparatus for optically monitoring the dosing of a liquid to be pipetted for an automatic analysis unit. The apparatus comprises a dosing device, comprising a pipetting needle for pipetting the liquid, a lighting device for illuminating a drop of the liquid adhering to the pipetting needle, a camera with a set of optics to capture an image of the drop of the liquid, and an evaluation device for characterizing the drop of liquid by means of an automatic analysis of the image of the drop of liquid.

CROSS REFERENCE TO RELATED APPLICATIONS

This claims priority to European Patent Application No. EP 19179863.6,filed Jun. 13, 2019, which is hereby incorporated. by reference hereinin its entirety for all purposes.

FIELD

The invention relates to an apparatus for optically monitoring thedosage of a liquid to be pipetted for an automatic analysis unit.

BACKGROUND

Numerous testing and analysis methods for determination of physiologicalparameters in bodily fluid samples or other biological samples are nowcarried out automatically in large numbers in automated analysis units,also known as in-vitro diagnostic systems.

Modern analysis units are able to perform a wide range of detectionreactions and analyses with one sample. In order to carry out aplurality of examinations automatically, various devices are requiredfor spatially transferring measurement cells, reaction containers andreagent containers, such as transfer arms with gripper function,conveyor belts or rotating transport wheels, as well as devices fortransferring liquids, such as pipetting devices. The devices comprise acontrol unit, which using appropriate software is able to plan andprocess the work steps for the desired analyses largely automatically.

Many of the analytical techniques used in such automated analysis unitsare based on optical methods. These methods enable the qualitative andquantitative testing of analytes, i.e., the substances to be detected ordetermined in samples. The determination of clinically relevantparameters, such as the concentration or activity of an analyte, isoften carried out by mixing a part of a sample with one or more testreagents in a reaction vessel, which may also be the measurement cell, aprocess which, for example, initiates a biochemical reaction or aspecific binding reaction that causes a measurable change in an opticalor other physical property of the assay.

For example, in automated analysis units used to examine biologicalbodily fluids, for example, the required reagents are placed in ameasuring cuvette using a pipetting device with a pipetting needle. Themeasuring cuvette is automatically moved into different positions with acuvette gripper inside the automatic analysis unit using a robot arm,which is part of a robot station. After the measurement, the measuringcuvette used is transported through a waste chute into a waste containerfor disposal.

In automatic analysis units, the process often involves liquids beingtransported in very small quantities. This is carried out, for example,by motorized displaceable pipettes, wherein the pipettes are operated bymotor-driven pumps. The pump generates a defined overpressure during thedelivery of the liquid and a defined negative pressure during thecollection of the fluid. The pipette is filled with an incompressiblesystem fluid to ensure that the pressure conditions or pressure changesspecified by the pump are recreated at the tip of the pipette withminimum loss, thus ensuring a high level of pipetting precision.

In medical devices such as diagnostic analyzers for automatic analysisof in-vitro samples, errors in the dosing of liquids and drop dispensingby means of the pipettes can lead to inaccuracies in the measurementsand incorrect measurement results. Such errors in the drop dispensingare caused, for example, by incorrect dosing at the dosing units.

Monitoring and subsequent verification in automatic analyzers hasusually been carried out up to now by using capacitive measurements todetermine the pipetted fluid quantity during the dispensing of theliquid to be dosed by the pipettor, or when immersing the pipette needlein the liquid being pipetted, in order to detect any deviations in thefill level due to, e.g., a malfunction of the dosing unit.Alternatively, pressure measurements would be performed during thedispensing of the liquid to be dosed by the pipette.

When dispensing, e.g., reagents onto an inclined wall in a vesselthrough a pipettor for optimal dispensing of very small amounts ofliquid, it may sometimes occur that there is no controlled fluidseparation and some or all of the fluid will stick to the pipette needleand not be dispensed properly. Even a capacitive measurement or pressuremeasurement is also difficult to achieve in this case, since due to thelack of an earth there is no counter electrode. The liquid runs down theinclined wall and is therefore no longer in contact with the pipette.For single dosing operations, it has therefore previously not beenpossible to subsequently check the changed filling level and hence toverify the correct function of the dosing unit.

The apparatuses from the prior art therefore do not always allow areliable monitoring of the dosing of pipetted liquids in automaticanalysis units.

SUMMARY OF THE INVENTION

An object of the invention is therefore to provide an improved apparatusand an improved method for monitoring the dosing of a pipetted fluid foran automatic analysis unit.

This object is achieved according to the invention by the objects andmethods described in the following.

It has been found that an improved apparatus for monitoring the dosageof a liquid to be pipetted for an automated analysis unit can beachieved by visually monitoring the dosing process using a camera andevaluating images of a drop of the liquid that adheres to the pipettingneedle and then characterizing the drop accordingly. The dosing itselfis usually monitored by means of an appropriately automated runningmonitor of the drive motor of the piston of an associated pumpingsystem. However, this cannot be used to indicate, for example, whetherthe entire volume of the liquid to be pipetted has actually beendispensed, e.g., into a reaction vessel, and whether the dosing has beencarried out correctly, or whether a significant residual amount of theliquid. remains stuck, e.g., to the tip of the pipetting needle. Opticalmonitoring has the advantage that the dosing process can be monitoredwith high precision. The monitoring is contactless and independent ofthe dosing process, so that interfering variables and inaccuracies whicharise, for example, due to lamella separation when the pipetting needleemerges from the liquid in capacitive level measurement, are avoided. Indosing processes in which a single quantity of liquid is dispensed andwhere capacitive measurement is not possible, for example because thesurrounding medium is not liquid, the apparatus according to theinvention enables for the first time a precise monitoring of the actualdosing process performed. Similar advantages are obtained for themonitoring of dosing processes in which liquid is dispensed onto aninclined wall and so drops of liquid can slide down the wall.

The subject matter of the present invention is in particular anapparatus for optically monitoring the dosing of a liquid to be pipettedfor an automatic analysis unit, the apparatus comprising:

a dosing device, comprising a pipetting needle for pipetting the liquid,a lighting device for illuminating a drop of the liquid adhering to thepipetting needle, a camera with a set of optics to capture an image ofthe drop of liquid, and an evaluation device for characterizing the dropof liquid by means of an automatic analysis of the image of the drop ofliquid.

Preferably, the evaluation device comprises one or more fieldprogrammable gate arrays (FPGAs) and/or a computer, wherein the computerpreferably comprises one or more graphics cards for image processing.

The camera is preferably connected to a computer and/or an FPGA and/or amicrocontroller or other suitable data processing machine.

Preferably, the apparatus according to the invention comprises a triggerdevice that can transmit a trigger signal to the camera to capture animage of the drop of liquid and/or to the evaluation device forcharacterizing the drop of liquid. Preferably, a continuous orquasi-continuous image recording or evaluation can be started by thetrigger signal.

Preferably, the trigger device comprises a light barrier, e.g., afork-type light barrier and/or a distance sensor, wherein the distancesensor determines a distance preferably by means of a time of flightmeasurement and/or triangulation. Preferably, the distance sensor canalso be an ultrasonic distance sensor, an inductive distance sensor,and/or a distance sensor based on a variable luminous flux.

The trigger signal can preferably be initiated by means of the triggerdevice in response to a movement of a piece of apparatus. The apparatuscan be, for example, a cuvette and/or the pipetting needle. Theapparatus is preferably part of an automatic analysis unit.

In another preferred embodiment, the trigger signal can also begenerated, for example, via a device which in turn controls the movementof another device.

The trigger device preferably comprises, e.g., an electronic and/oroptical component for triggering an operation, preferably a switchingoperation.

In a preferred design, the lighting device comprises a ring illuminator.

In another preferred design, the ring illuminator is arranged on thecamera and/or optics.

In another preferred design, the lighting device comprises a mirror.Preferably, the mirror is arranged such that the drop of liquid can beimaged via the mirror using the optics of the camera.

In another preferred design, the lighting device comprises a beamsplitter. Preferably, the beam splitter is arranged such that the dropof liquid can be imaged via the beam splitter using the optics of thecamera. The illumination of the drop of the liquid is advantageouslycoupled in by the lighting device using the beam splitter.

In another preferred design, the lighting device comprises at least onelight source, preferably more than one light source, particularlypreferably three light sources.

A further subject of the invention is a method for optically monitoringthe dosing of a liquid to be pipetted for an automatic analysis unit byacquiring an image of a drop of the liquid, preferably using anapparatus according to the invention for optically monitoring the dosingof a liquid to be pipetted, the method comprising the following steps:

-   -   dosing the liquid by pipetting using the dosing device,    -   using a lighting device to illuminate a drop of the liquid        adhering to the pipette needle after the dosing is completed,    -   acquiring the image of the drop of the liquid using the optics        and the camera,    -   characterizing the drop by means of the evaluation device and        the automatic analysis of the images of the drop of liquid.

Preferably, the acquisition of the image of the drop is initiated by atrigger signal from a trigger device, which is transmitted to the cameraby the trigger device. Alternatively, the acquisition can also beperformed continuously, independently of a trigger signal.

Preferably, the characterization of the drop by means of the evaluationdevice is initiated by a trigger signal, from a trigger device, which istransmitted to the evaluation device by the trigger device.Alternatively, the characterization of the drop can also be performedcontinuously, independently of a trigger signal.

Preferably, a continuous or quasi-continuous image recording orevaluation can be started by the trigger signal. The image recordingand/or evaluation is preferably carried out until a further triggersignal triggers a corresponding termination, or until a predefinedperiod of time has elapsed.

The trigger signal is preferably initiated by means of the triggerdevice in response to a movement of a piece of apparatus. The apparatuscan be, for example, a cuvette and/or the pipetting needle. Theapparatus is preferably part of an automatic analysis unit.

In another preferred embodiment, the trigger signal is generated via adevice which in turn controls a movement of another device.

In a preferred implementation of the method, the characterization of thedrop of liquid comprises the determination of the outline of the drop.

In a further preferred implementation of the method, thecharacterization of the drop of liquid comprises the determination ofthe volume of the drop.

In a further preferred implementation of the method, the determinationof the volume of the drop of liquid comprises at least one assumptionconcerning the symmetry of the drop. The drop is preferably assumed tobe symmetrical about at least one rotation axis.

In a further preferred implementation of the method, thecharacterization of the drop of liquid comprises a contactless detectionof the quantity of liquid in the drop. Preferably, the detected quantityof liquid in the drop is also used to determine whether the dosing ofthe liquid has been performed correctly, and/or a quality of the dosingis determined, which is preferably carried out by means of theevaluation device. For example, if the volume of liquid detected exceedsa predefined absolute limit or a predefined variable limit, whichdepends, e.g., on the quantity of liquid to be pipetted, then the liquiddosing has not proceeded correctly; otherwise it has proceededcorrectly. If the dosing has not taken place in the proper manner, anappropriate characterization of the dosing process is advantageouslyperformed automatically and communicated to the laboratory personnel viaa corresponding display on a monitor or on a paper printout, forexample. Alternatively, a corresponding measurement process can also beautomatically aborted and restarted, for example.

Alternatively, the detected quantity of liquid of the drop isadvantageously used as a correction value and the actual dosing that wascarried out is determined by deducting the detected quantity of liquidin the drop from a planned dosage. Optionally, an appropriate additionaldosing can then advantageously be carried out, which adds the missingamount of liquid. This has the advantage that incorrect measurements areavoided and/or can be identified as such.

In a preferred implementation of the method, the determination ofwhether the liquid dosing has proceeded correctly and/or of the qualityof the dosing is made by means of machine learning and/or comprises theuse of a machine learning system.

In a preferred embodiment, the volume of the drop adhering to thepipetting needle is determined firstly by weighing out the correspondingquantity of liquid and then comparing it using image data for aplurality of drops. The image data comprise the images of the drops. Acalibration is therefore preferably carried out in advance. This ispreferably followed by assigning an appropriate quality to the dosing ofthe liquid using machine learning.

Preferably, a method according to the invention is carried out partiallyor completely by means of an apparatus according to the invention. Thispreferably involves capturing the image of the drop of liquid using anapparatus according to the invention.

Another subject of the invention is an analysis unit which comprises anaforementioned apparatus according to the invention for opticallymonitoring the dosing of a liquid to be pipetted and/or which isconfigured such that it can carry out a method according to theinvention. The analysis unit also advantageously comprises an automaticcuvette gripper and/or an automatic pipettor.

A further subject of the invention is the use of an apparatus accordingto the invention for optically monitoring a dosing of a liquid to bepipetted in an automatic analysis unit, wherein the automatic analysisunit preferably comprises an automatic cuvette gripper and/or anautomatic pipettor.

For the purposes of the invention, a “sample” means the material that ispresumed to contain the substance (the analyte) to be detected. Inparticular, the term “sample” covers biological fluids of humans oranimals such as blood, plasma, serum, sputum, exudate, bronchoalveolarlavage, lymphatic fluid, synovial fluid, seminal fluid, vaginal mucus,feces, urine, CSF, but also appropriately prepared tissue or cellculture samples, e.g., by homogenization or cell lysis for thephotometric, preferably nephelometric analysis. In addition, forexample, liquids or tissues of vegetable origin, forensic samples, waterand sewage samples, foodstuffs, medicinal products may also act assamples, which may need to be suitably pre-treated before the analysis.

A quantitative test measures the amount, concentration or activity ofthe analyte in the sample. The term “quantitative test(ing)” alsoincludes semi-quantitative methods that can only measure the approximateamount, concentration or activity of the analyte in the sample, or canonly be used to indicate relative quantities, concentrations oractivity. A qualitative test is the detection of the presence or absenceof the analyte in the sample, or the indication that the amount,concentration or activity of the analyte in the sample is above or belowone or more specific threshold values.

For example, a measuring cuvette is a cuvette or a reaction vessel madeof glass, plastic or metal. The measuring cuvette is advantageouslymanufactured from optically transparent materials, which can beparticularly advantageous when using optical analysis methods.

The terms “measuring cuvette” and “cuvette” are used interchangeably andrefer to the same object.

The terms “analysis unit” and “analyzer” are used here interchangeablyand refer to the same object.

A drop of a liquid is a quantity of the liquid that can be present, forexample, in the form of a film of liquid, in shapes similar to the shapeof bulbs, or as spherical droplets of liquid. The quantity of the liquidpreferably involves quite small quantities of liquid, which can be,e.g., in the range of 1 to 100 microliters, preferably in the range of 5to 10 microliters.

The camera preferably comprises a digital recording device comprising acharge-coupled device (CCD) chip or a plurality of CCD chips. Thedigital recording device is particularly preferably based on aComplementary Metal-Oxide-Semiconductor (CMOS) technology and/orcomprises a CMOS chip. The camera may also preferably be a digitalrecording device.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in further detail byreference to drawings. In the figures:

FIGS. 1, 2, 3, and 4 schematically show the structure of differentadvantageous embodiments of an apparatus for optically monitoring adosing of a liquid to be pipetted for an automatic analysis unit.

Equivalent parts are labeled with the same reference signs in allfigures.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus (1) according to FIGS. 1 to 4 is embedded in an analysisunit, not shown in detail, which is designed to perform a wide range ofanalyses of samples. To this end, the automatic analysis unit comprisesa plurality of pipetting devices and transport devices, not shown, inaddition to a control unit for the automated evaluation of the analyses,and an evaluation device (6) for characterizing a drop (4) of a liquidadhering to the dosing device (2) by means of an automatic evaluation ofan image of the drop (4) of liquid. Each apparatus (1) is designed foroptically monitoring the dosing of a liquid to be pipetted for anautomated analysis unit.

In the embodiment of the apparatus (1) shown in FIG. 1 , a drop (4) of aliquid is pipetted by means of the dosing device (2). The drop (4)adheres to the tip of a pipetting needle. Below the drop (4) a camera(5) with a set of optics is arranged. The drop is directly illuminatedfrom below at an angle by means of a lighting device (3), wherein thelighting device (3) comprises a light source (10).

In the embodiment of the apparatus (1) shown in FIG. 2 , a drop (4) of aliquid is pipetted by means of the dosing device (2). The drop (4)adheres to the tip of a pipetting needle. At the level of the drop (4),a camera (5) with an optical system is arranged to one side. The drop isilluminated from the side by means of a lighting device (3), which isdesigned as a ring illuminator (7). The ring illuminator (7) is arrangedon the optics of the camera (5).

In the embodiment of the apparatus (1) shown in FIG. 3 , a drop (4) of aliquid is pipetted by means of the dosing device (2). The drop (4) islocated at the tip of a pipetting needle. Slightly below the level ofthe drop (4), a camera (5) with a set of optics is arranged to one side.The drop is illuminated from the side by means of a lighting device (3),which comprises a ring illuminator (7) arranged on the optical system ofthe camera (5), and two other light sources (10). Both the ringilluminator (7) and the two other light sources (10) directly illuminatethe drop (10). Further, an optical mirror (8) is located below the drop(4) at an angle to the optical axis of the camera (5). The imaging ofthe drop by means of the optics of the camera (5) is carried out via themirror (8).

In the embodiment of the apparatus (1) shown an FIG. 4 , a drop (4) of aliquid is pipetted by means of the dosing device (2). The drop (4)adheres to the tip of a pipetting needle. At the level of the drop (4),a camera (5) with an optical system is positioned to one side. A beamsplitter (9) is arranged between drop (4) and camera (5). Above the beamsplitter (9), a lighting device (3) is provided, which comprises a lightsource (10). The light emerging from the light source is deflected bymeans of the beam splitter (9) and strikes the drop (4) along theoptical axis of the camera (5) and illuminates it. The drop (4) isimaged through the beam splitter (9) using the optics of the camera.

LIST OF REFERENCE SIGNS

-   1 apparatus-   2 dosing device-   3 lighting device-   4 drop-   5 camera-   6 evaluation device-   7 ring illuminator-   8 mirror-   9 beam splitter-   10 light source

The invention claimed is:
 1. An apparatus for optically monitoring adosing of a liquid to be pipetted for an automatic analysis unit, theapparatus comprising a dosing device comprising a pipetting needle forpipetting the liquid, a lighting device for illuminating a drop of theliquid adhering to the pipetting needle, a camera with a set of opticsfor capturing an image of the drop of the liquid only adhering to thepipetting needle, the camera arranged to a side of the drop of theliquid and the pipetting needle, and an evaluation device forcharacterizing the drop of the liquid via an automatic analysis of theimage of the drop of the liquid and for using a detected quantity of thedrop as a correction value to determine an additional dosing in responseto the detected quantity of the drop not equaling a planned dosage. 2.The apparatus as claimed in claim 1, wherein the lighting devicecomprises a ring illuminator.
 3. The apparatus as claimed in claim 2,wherein the ring illuminator is located on the camera or the optics. 4.The apparatus as claimed in claim 1, wherein the lighting devicecomprises a mirror.
 5. The apparatus as claimed in claim 1, wherein thelighting device comprises a beam splitter.
 6. The apparatus as claimedin claim 1, wherein the lighting device comprises at least one lightsource.
 7. A method for optically monitoring the dosing of a liquid tobe pipetted for an automatic analysis unit by acquiring an image of adrop of the liquid, the method comprising the following steps: dosing ofthe liquid by pipetting using a dosing device, using a lighting deviceto illuminate a drop of the liquid adhering to the pipette needle afterthe dosing is completed, acquiring the image of the drop of the liquidonly adhering to the pipetting needle from a side of the drop of theliquid and the pipetting needle using a set of optics and a camera,characterizing the drop via an evaluation device and an automaticanalysis of the image of the drop of the liquid, and an additionaldosing of the liquid by pipetting using the dosing device to add anamount of the liquid in response to the characterizing determining thata detected quantity of the liquid in the drop is less than a planneddosage.
 8. The method as claimed in claim 7, wherein thecharacterization of the drop of the liquid comprises the determinationof the outline of the drop.
 9. The method as claimed in claim 7, whereinthe characterization of the drop of the liquid comprises thedetermination of the volume of the drop.
 10. The method as claimed inclaim 9, wherein the determination of the volume of the drop of theliquid comprises at least one assumption about the symmetry of the drop.11. The method as claimed in claim 7, wherein via the characterizationof the drop of the liquid, the quantity of liquid in the drop isdetected in a contactless manner.
 12. The method as claimed in claim 11,wherein the detected quantity of liquid in the drop is used to determinewhether the dosing of the liquid has been performed correctly.
 13. Themethod as claimed in claim 12, wherein the determination is carried outby machine learning or comprises the use of a machine learning system.14. The method as claimed in claim 7, wherein the image of the drop ofthe liquid is acquired via an apparatus comprising: the dosing devicecomprising a pipetting needle for pipetting the liquid, the lightingdevice, the camera with the set of optics, and the evaluation device,wherein the entire method is carried out via the apparatus.
 15. Anautomatic analysis unit, wherein the automatic analysis unit comprisesan apparatus as claimed in claim
 1. 16. An automatic analysis unit,wherein the automatic analysis unit is configured to execute a method asclaimed in claim 7, the automatic analysis unit having an automaticcuvette gripper or an automatic pipettor.
 17. The apparatus as claimedin claim 1, wherein the lighting device comprises at least three lightsources.
 18. The method as claimed in claim 10, wherein the at least oneassumption includes the drop being symmetric about at least onerotational axis.
 19. The method as claimed in claim 11, wherein aquality of the dosing is determined.
 20. The method as claimed in claim19, wherein the quality of the dosing is determined via the evaluationdevice.